Resolve "Follow-up from "Add medium type, as new property (air, water, rock...)""

Closes #319

See merge request !399

make conex module fit for multiple events. Added init function

See merge request !385

Add tracking of particle times to observation plane writer

See merge request !394

Change logging level for InteractionHistogram::fill from info to debug

See merge request !393

Enable C++ syntax highlighting for .inl files on Gitlab

See merge request AirShowerPhysics/corsika!398

Bug in Cascade.inl

See merge request !397

Resolve "CI sometimes fails to run tests"

Closes #451

See merge request !395

Make  the CORSIKA_DATA environment variable optional.

See merge request !389